Photography has evolved tremendously over the last century, but has always incurred needs for manipulation of the captured images. In some cases, the manipulation seeks to improve some quality of the image relative to what a human subject might perceive. In other cases, the manipulation seeks to ameliorate artifacts of various types that cause the captured image to deviate from images corresponding to those a human subject might perceive.
The dynamic range of photographic media, including photodetectors employed in digital photography, is limited in comparison to the dynamic range of natural vision processes. As a result, there may be need to enhance illumination when taking a photograph. One convenient and highly portable approach suitable for close-range photography is to synchronize a brief but bright burst of light with the image capture process. In many cases, the illumination source is a flash bulb that is immediately adjacent the camera lens.
However, when the photograph includes faces, substantial reflection from the subject's retinae can occur depending on the relative position of the illumination source, the lens and the photographic subjects. This is exacerbated by dilation of the subject's pupils in response to the ambient illumination conditions that also made the added illumination desirable in order to be able to take the picture. In human subjects, such retinal reflections often result in unnatural reddening of the pupil region of the subject's eyes or a halo of red in that vicinity; in other types of animals, other colors may result (e.g., green in feline eyes, resulting from a reflective structure behind the retina known as a tapetum; other possibilities depend on the structure etc. of the subject's eyes).
Various types of editing have been employed in the past to address these distortions. Darkroom techniques historically have been employed for photographs using emulsion and other photochemical image recording technologies. Digitization of such images and direct digital image capture led to techniques requiring powerful processors and sophisticated software requiring extensive training and experience of human operators to achieve desired image manipulation goals.
However, the advent of digital photography, coupled with increasingly powerful microprocessors, permit editing of digital images in a personal computer. One exemplary product for such manipulation is known as “iPhoto”, available from Apple, 1 Infinite Loop, Cupertino, Calif. 95014, tel. (408) 996-1010. Other exemplary products are known as “Picture It” and “PhotoDraw”, developed by Microsoft Corporation, Redmond, Wash. These products require user input in order to be able to identify target regions within the image that include red-eye artifacts.
Another technique for red-eye amelioration is described in U.S. Pat. No. 6,009,209, entitled “Automated Removal Of Red Eye Effect From A Digital Image”, issued to Acker et al., assigned to the assignee of this disclosure and hereby incorporated herein by reference. This patent describes an apparatus and method for automatically editing a digital color image by parsing the discoloration into regions and re-coloring the area of discoloration based on attributes of the discoloration. This technique also relies on user input to identify and correct red-eye artifacts in digital images.
Much research has been devoted to rendering digital photography user-friendly and to enable those having relatively little training or sophistication to provide high quality images. However, automatic compensation of image distortion due to the red-eye artifact continues to be desirable, particularly for photographic instruments intended to foster broad market acceptance across a user base reflecting different degrees of user sophistication.